There are many instances in which a human bone becomes damaged or deficient, typically due to either arthritis or a traumatic injury. A bone may also show signs of wear due to repetitive use over time.
It is now becoming relatively common for a person to have his/her bearing surface of a joint replaced with a synthetic implant to provide relief from the pain caused by contact of the damaged bearing surfaces of the bones that form the joint. When treating a traumatic injury, such as a fracture, it has also become relatively common to insert a metal rod into the bone to immobilize the fractured bone segments and allow the bone to heal properly.
At times, it may be more advantageous to graft another material onto a damaged portion of a person's bone to either repair the damage or to allow the bone the opportunity to properly heal. There are many types of grafts that can be placed onto a damaged surface of a person's bone, including an autograft, which utilizes a bone from another portion of a person's body to be grafted onto the damaged portion of the bone. An autograft material is the least likely graft to experience rejection by the body.
The next least likely type of graft to be rejected is an allograft, which consists of grafting a portion of another person's bone onto the damaged bone of a patient. Unlike an autograft, which takes bone from the same person to be grafted onto the same person's damaged bone, an allograft is contains material from another human's bone that can be grafted onto the damaged surface of a patient's bone.
A xenograft is a graft of a bone from another species into a patient. One typical xenograft would be, for instance, utilizing a bovine bone to graft onto a human bone. There are other types of grafts that can be utilized, such as synthetic or artificial bones made out of calcium phosphate or a combination of bioglass with calcium phosphate. Finally, plastics may also be utilized as a bone graft.